【发布时间】：2013-04-28 09:30:29
【问题描述】：
请给我一个代码可以恢复 GPS 位置或每隔 n 分钟，我测试了几个代码但没有结果
请有人给我一个教程或一个小程序，我真的卡住了
public final class TrackListener implements LocationListener {
private final Context mContext;
public boolean isGPSEnabled = false;
boolean isNetworkEnabled = false;
public boolean canGetLocation = false;
Location location; // location
double latitude; // latitude
double longitude; // longitude
// The minimum distance to change Updates in meters
private static final long MIN_DISTANCE_CHANGE_FOR_UPDATES = 10; // 10 meters
// The minimum time between updates in milliseconds
private static final long MIN_TIME_BW_UPDATES = 1000 * 60 * 1; // 1 minute
// Declaring a Location Manager
protected LocationManager locationManager;
public TrackListener(Context context) {
this.mContext = context;
getLocation();
}
public Location getLocation() {
try {
locationManager = (LocationManager) mContext
.getSystemService(Contexts.LOCATION_SERVICE);
isGPSEnabled = locationManager
.isProviderEnabled(LocationManager.GPS_PROVIDER);
Log.v("isGPSEnabled", "=" + isGPSEnabled);
isNetworkEnabled = locationManager
.isProviderEnabled(LocationManager.NETWORK_PROVIDER);
Log.v("isNetworkEnabled", "=" + isNetworkEnabled);
if (isGPSEnabled == false && isNetworkEnabled == false) {
} else {
this.canGetLocation = true;
if (isNetworkEnabled) {
locationManager.requestLocationUpdates(
LocationManager.NETWORK_PROVIDER,
MIN_TIME_BW_UPDATES,
MIN_DISTANCE_CHANGE_FOR_UPDATES, this);
Log.d("Network", "Network");
if (locationManager != null) {
location = locationManager
.getLastKnownLocation(LocationManager.NETWORK_PROVIDER);
if (location != null) {
latitude = location.getLatitude();
longitude = location.getLongitude();
}
}
}
if (isGPSEnabled) {
if (location == null) {
locationManager.requestLocationUpdates(
LocationManager.GPS_PROVIDER,
MIN_TIME_BW_UPDATES,
MIN_DISTANCE_CHANGE_FOR_UPDATES, this);
Log.d("GPS Enabled", "GPS Enabled");
if (locationManager != null) {
location = locationManager
.getLastKnownLocation(LocationManager.GPS_PROVIDER);
if (location != null) {
latitude = location.getLatitude();
longitude = location.getLongitude();
}
}
}
}
}
} catch (Exception e) {
e.printStackTrace();
}
return location;
}
public void stopUsingGPS() {
if (locationManager != null) {
locationManager.removeUpdates(TrackListener.this);
}
}
public double getLatitude() {
if (location != null) {
latitude = location.getLatitude();
}
return latitude;
}
public double getLongitude() {
if (location != null) {
longitude = location.getLongitude();
}
return longitude;
}
public boolean canGetLocation() {
return this.canGetLocation;
}
public void showSettingsAlert() {
AlertDialog.Builder alertDialog = new AlertDialog.Builder(mContext);
alertDialog.setTitle("GPS is settings");
alertDialog
.setMessage("GPS is not enabled. Do you want to go to settings menu?");
alertDialog.setPositiveButton("Settings",
new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int which) {
Intent intent = new Intent(
"ACTION_LOCATION_SOURCE_SETTINGS");
mContext.startActivity(intent);
}
});
alertDialog.setNegativeButton("Cancel",
new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int which) {
dialog.cancel();
}
});
alertDialog.show();
}
public void onLocationChanged(Location location) {
if (location != null) {
latitude = location.getLatitude();
longitude = location.getLongitude();
}
}
@Override
public void onProviderDisabled(String provider) {
Toast.makeText(Contexts.getAppContext(), "GPS Disable ",
Toast.LENGTH_LONG).show();
}
@Override
public void onProviderEnabled(String provider) {
Toast.makeText(Contexts.getAppContext(), "GPS enabled",
Toast.LENGTH_LONG).show();
}
@Override
public void onStatusChanged(String provider, int status, Bundle extras) {
}
但是在课堂活动中调用“getLocation()”时，我发现了一个致命问题
04-28 08:41:55.126: W/dalvikvm(16004): threadid=1: thread exiting with uncaught exception (group=0x40015560)
04-28 08:41:55.186: E/AndroidRuntime(16004): FATAL EXCEPTION: main
04-28 08:41:55.186: E/AndroidRuntime(16004): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.testss/com.example.testss.MainActivity}: java.lang.NullPointerException
04-28 08:41:55.186: E/AndroidRuntime(16004): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1647)
04-28 08:41:55.186: E/AndroidRuntime(16004): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1663)
04-28 08:41:55.186: E/AndroidRuntime(16004): at android.app.ActivityThread.access$1500(ActivityThread.java:117)
04-28 08:41:55.186: E/AndroidRuntime(16004): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:931)
04-28 08:41:55.186: E/AndroidRuntime(16004): at android.os.Handler.dispatchMessage(Handler.java:99)
04-28 08:41:55.186: E/AndroidRuntime(16004): at android.os.Looper.loop(Looper.java:123)
04-28 08:41:55.186: E/AndroidRuntime(16004): at android.app.ActivityThread.main(ActivityThread.java:3683)
04-28 08:41:55.186: E/AndroidRuntime(16004): at java.lang.reflect.Method.invokeNative(Native Method)
04-28 08:41:55.186: E/AndroidRuntime(16004): at java.lang.reflect.Method.invoke(Method.java:507)
04-28 08:41:55.186: E/AndroidRuntime(16004): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
04-28 08:41:55.186: E/AndroidRuntime(16004): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
04-28 08:41:55.186: E/AndroidRuntime(16004): at dalvik.system.NativeStart.main(Native Method)
04-28 08:41:55.186: E/AndroidRuntime(16004): Caused by: java.lang.NullPointerException
04-28 08:41:55.186: E/AndroidRuntime(16004): at com.example.testss.MainActivity.onCreate(MainActivity.java:27)
04-28 08:41:55.186: E/AndroidRuntime(16004): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
04-28 08:41:55.186: E/AndroidRuntime(16004): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1611)
04-28 08:41:55.186: E/AndroidRuntime(16004): ... 11 more
04-28 08:46:55.255: I/Process(16004): Sending signal. PID: 16004 SIG: 9
【问题讨论】：
-
你有访问GPS的权限吗？
-
是的，我做了
-
您在
MainActivity第 27 行中有一个NullPointerException。与您发布的代码无关。正确初始化您的对象。 -
了解如何使用调试器，在这种情况下确定错误的位置非常有用。